WO1992018289A1

WO1992018289A1 - Impact tool

Info

Publication number: WO1992018289A1
Application number: PCT/SE1992/000228
Authority: WO
Inventors: Ivan Ilyes
Original assignee: Skandinavisk Energi Modul S.E.M. Ab
Priority date: 1991-04-12
Filing date: 1992-04-08
Publication date: 1992-10-29
Also published as: SE9101106L; SE9101106D0; AU1455392A; SE468241B

Abstract

Impact tool comprising a substantially cylindrical housing (1) with a projecting, tool-carrying shaft (11), and a handle (3) connected with the housing. The housing and the handle accomodate an impact mechanism comprising a wheel device (4) with projections (13), which is rotatably mounted in the housing. Each projection (13) is formed with an impact surface (14). The impact mechanism also comprises striking means (5) with a hammering member (7) which has an impact surface (8) for engaging the impact surface (14), and a compression spring (6) mounted in the handle (3) and engaging the hammering member (7). The invention is characterised in that the hammering member (7) is supported in the handle (3) for rectilinear motion in the axial direction of the handle, that the wheel device (4) is formed with a limited number of projections (13), that the wheel device is provided with superposed, projecting cam means (15) which are arranged in the direction of rotation after each surface (14), and that the hammering member (7) is provided with a superposed, projecting cam means (9) for engaging the respective cam means (15) of the wheel device (4), when the impact surface (8) of the hammering member (7) is disengaged from the impact surface (14) of the coacting projection (13).

Description

IMPACT TOOL

The present invention relates to an impact tool com¬ prising a substantially cylindrical housing with a pro- jecting, tool-carrying shaft, and a handle connected with the housing. The housing and handle accommodate an impact mechanism comprising a wheel device rotatably mounted in the housing and formed with projections. Each projection has an impact surface. The impact mechanism also comprises striking means with a hammering member having an impact surface, and a compression spring mounted in the handle and engaging the hammering member. The tool-carrying shaft is attached to the centre of the wheel device. The impact surface of the hammering member engages the impact surface of one projection, when the impact tool is unloaded- This engagement also occurs during the inital rotation of the housing relative to the wheel device, when the handle is operated in order to rotate the tool-carrying shaft. When the tool-carrying shaft is nonrotatable, the spring is tensioned and after a fixed angle of rotation of the hous¬ ing relative to the wheel device, the impact surface of the hammering member is disengaged from the impact surface of said projection. Subsequently the bias of the spring then causes the impact surface of the hammering member to strike the impact surface of the succeeding projection.

More precisely, the invention relates to a hand tool with a spring-oper&ted impact mechanism for loosening (or tightening) nuts, bolts etc.

An impact tool having the above features is disclosed in German Offenlegungsschrift 1,403,433. This impact tool comprises a cylindrical weight member which is rotatable relative to the tool handle and which pivotably supports three hammering members which are spring-loaded in radial direction for engaging the wheel device which supports the tool-carrying shaft. The wheel device is fitted with a large number of teeth with which the hammering members cooperate, for which reason the stroke of the tool, i.e. the distance between neighbouring teeth, is small. Since the cylindrical weight member has a considerable wall thickness, the diameter of the wheel device and, thus, also the moment arm (the distance from the flank of a tooth to the shaft of the wheel device) are limited. More¬ over, the hammering members effecting the stroke movement is of fragile design owing to their small thickness, pivotable mounting and spring load. Finally, the prior-art impact tool comprises a plurality of components that may be damaged or get caught owing to the impact forces pro¬ duced in the tool.

US Patent Specification 2,661,647 discloses an impact tool similar to the prior-art tool as described above, but comprises an adjustable coil spring at the handle, instead of a compression spring. This impact tool consists of fewer components, but suffers from the same deficiencies as the above tool. Moreover, the impact mechanism in these prior-art tools is not completely protected by a housing since the cylindrical weight members are arranged exter- nally.

The.object of the present invention is to provide an impact tool having high torque and high impact force.

A further object of the invention is to provide an impact tool which is substantially insusceptible to strik- ing forces and is inexpensive to design and mount.

One more object of the invention is to provide a robust tool with a limited number of components, whose mechanism is fully enclosed in a protective housing and whose power is adjustable. According to the invention, these objects are achiev¬ ed by an impact tool as described above, which is charac¬ terised in that the hammering member is supported in the handle for rectilinear motion in the axial direction of the handle, that the wheel device comprises a limited num- ber of projections, that the wheel device is provided with superposed, projecting cam means which are arranged in the direction of rotation after each impact surface, and that the hammering member is provided with a superposed, pro¬ jecting cam means for engaging the respective cam means of the wheel device, when the impact surface of the hammering member is disengaged from the impact surface of the coact- ing projection.

Further developments of the invention appear from the features stated in the subclaims.

Preferred embodiments of the invention will now be described for the purpose of exemplification, with refe- rence to the accompanying drawings in which:

Fig. 1 is top plan view, partly in section, of a pre¬ ferred embodiment of the impact tool according to the invention,

Fig. 2 is a cross-sectional view along the line A-A illustrating on an enlarged scale the vertical orientation of the coacting cam means of the impact mechanism.

Fig. 3 is an enlarged longitudinal view of part of the impact mechanism in its unloaded state.

Fig. 4 is a view similar to the one in Fig. 3 of the impact mechanism, when the hammering member has been maxi¬ mally pushed back by the wheel device, and

Fig. 5 is a view similar to those in Figs 3 and 4 of the impact mechanism, when the hammering member has been maximally pushed back by a cam means of the wheel device, and the hammering member is just being released in order to strike a projection of the wheel device.

With reference first to Figs 1 and 2, the impact tool according to the invention comprises a substantially cylindrical housing 1 with a cover 2 (indicated by dash- dot lines in Fig. 2) which preferably is releasably attached to the circumferential wall of the housing by means of a screw joint or the like. As is apparent from Fig. 2 , the bottom of the housing and the cover are flat and extend in parallel with one another. A handle 3 is rigidly attached to the housing 1, preferably by means of a welded joint as shown in Fig. 1. The handle can also be releasably attached to the housing by a threaded joint or the like. The housing 1 and the handle 3 jointly enclose an impact mechanism consisting of a wheel device 4 and striking means 5.

The striking means 5 comprises a spring means 6, preferably a compression spring in the form of a helical spring as indicated in Fig. 1, or in the form of a gas spring or the like. The spring 6 is enclosed in the handle 3 and its one end engages a stop member (not shown) at the outer end of the handle. This stop member is advantageous- ly adjustable in the longitudinal direction of the handle, thereby permitting adjustment of the bias of the spring 6. The stop member may consist of opposite pairs of holes in the handle which cooperate with a through pin or bolt extending transversely of the longitudinal axis of•the handle for step-by-step adjustment of the bias. If desir¬ ed, the stop member can be a cylindrical body with exter¬ nal threads engaging matching threads inside the handle, and have a groove for operating an external tool, e.g. a slot for turning the body by means of a screw driver. This renders continuous adjustment of the spring bias possible. Of course it is also possible to let the above-mentioned end of the spring engage a closure at the end of the handle 3, in which case it may be necessary to attach the handle to the housing 1 by means of a threaded joint. The other end of the spring 6 engages a hammering member 7 which is reciprocable in the handle in the longi¬ tudinal direction thereof and in the casing in tangential direction. The hammering member 7 is made of high quality steel to withstand a large number of blows and has a con- siderable weight for producing an appropriate striking effect. To reduce the cost of the hammering member, it may be designed as a separate hammer body and a separate weight member made of some less expensive or heavier metal and mounted between the hammering member and the spring 6 (not shown). The end of the hammering member, which pro¬ jects into the housing 1, is connected with a suitably designed impact surface 8, and a projecting cam means 9 is welded to or cast integrally with this end, see especiall Fig. 2.

The wheel device 4 is rotatably mounted in the hous¬ ing 1 and in the cover 2, e.g. by means of a central pin 10 and a tool-carrying shaft 11 which project perpendicu¬ larly from the wheel device and are integrally formed therewith. The pin 10 and the shaft 11 which project from the cover can, if desired, be replaced by a separate shaf of noncircular cross-section, e.g. square cross-section, which is received in an axially displaceable manner in a correspondingly designed, central opening in the wheel device (not shown). In this case, the tool-carrying shaft 11 must be supported by special bearing means in the cove and in the bottom of the housing. At least one shaft end 12 is designed with a cross-section that matches spanner attachments, bit holders and similar tool attachments for tightening nuts, bolts etc.

Furthermore, the wheel device 4 is formed with a limited number of arms or projections 13, in the shown embodiment three, equidistantly spaced from each other in circumferential direction and identical with each ther. Each projection 13 is formed at its outer end with a pro¬ jecting impact surface 14 which is designed as a cam sur¬ face and extends along the outermost portion of the pro- jection 13, as is best seen in Figs 3 and 4. In the illu¬ strated embodiment, the wheel device is adapted to be rotated clockwise in the striking operation, and therefor the impact surfaces 14 are arranged on the left side of each projection 13. The opposite, right side of the pro- jections and the width thereof are such that the hammerin member 7, during its striking motion, is free to pass between each projection 13 and the inner wall of the hous ing 1, as shown in Figs 2 and 3. Fig. 2 also shows that the hammering member 7 and the wheel device 4 are oriente in the same plane, and they are preferably made of the same material. Like the hammering member 7, the wheel device 4 is fitted with superposed, projecting cam means 15 which are arranged on each projection 13 on the side opposite the impact surface 14. The cam means 15 are identical in respect of design and position and are arranged at a fixed distance from the outermost portion of each projec¬ tion 15, the cam means further having a cam surface 16 and an undercut surface 17. The cam means 15 of the wheel device, which are also welded to or cast integrally with the wheel device, are arranged in the same plane as the cam means 9 of the hammering member 7 (see Fig. 2), with which the cam means 15 of the wheel device are adapted to coact, ^%as will be described below. If required, the cam means 9 can be provided with a further, superposed cam means which projects therefrom and thus is arranged in a plane above the cam means 9, but under the cover 2 (not shown). In this case, each cam means 15 is provided with an additional, superposed cam means which can be moved into engagement with the additional cam means of the cam means 9, when this is disengaged from the respective cam means 15. If required, additional cam means in the same plane can be stacked in an offset fashion on the subja¬ cent cam means, as will be described below.

The impact tool according to the invention functions in the manner that will be described below with reference to Figs 3-5.

To loosen a nut, bolt or the like, a suitable tool is attached to the shaft end 12 and moved into engagement with the nut. The coacting components of the impact echa- nism, i.e. the striking means 5 and the wheel device 4, are then oriented as shown in Figs 1-3. The handle 3 is turned in the direction indicated by arrow 18. Provided that the nut cannot be moved, the tool-carrying shaft 11 then fixes the wheel device 4 against rotation, the handle 3 and the housing 1 being turned relative to the wheel device 4. The spring 6 presses the impact surface 8 of the hammering member 7 against the impact surface 14 of the wheel device. During continued turning of the handle 2, the hammering member 7 is pressed further into the handle owing to the engagement between the impact surfaces 8 and 14, against the action of the spring 6 which is conti- nuously being compressed and tensioned. The direction of motion of the hammering member is indicated by arrow 19 in Fig. 1. During this initial turning motion, the impact surface 8 slides along the impact surface or cam surface 14 in the direction of the outer end of the projection 13. Fig. 4 shows the maximum pushing back of the hammer¬ ing member 7 into the handle 3 that can be effected by means of the projections 13 of the wheel device 4.

However, it is possible to push back the hammering member further into the handle and, as a result, obtain additional spring force and length of stroke of the hammer ing member, which, taken together, essentially increases the performance of the impact tool.

Instead of the hammering member 7 being disengaged from the projection and being caused by the spring force to hit the succeeding projection during continued turning of the housing 1 in relation to the immovable wheel device 4 after the situation illustrated in Fig. 4, the cam sur¬ face 20 of the cam means 9 fitted on the hammering member 7 will be caused to engage the cam surface 16 of the cam means 15 arranged on the coacting projection 13. Because of the design of the cam means 9 and 16 and the position thereof on the hammering member and the wheel device, respectively, the cam surfaces 16 and 20 of the cam means will slide towards one another during continued turning of the housing 1, the hammering member being pushed back fur¬ ther into the handle, see Fig. 5.

Fig. 5 shows that the turning of the housing 1 in relation to the wheel device 4 has now been effected to such an extent that the hammering member has been maxi- ally pushe back and just is being disengaged from the wheel device. Since the cam means has an undercut surface 17 connecting with the cam surface 16, the hammering mem- ber is free to be thrust, by forces exerted by the spring 6, against the succeeding projection 13a. It should be noted that at this moment the projection 13a is oriented perpendicular to the direction of motion of the hammering member, which is indicated by arrow 21 in Fig. 1. This results in a maximum torque being applied on the tool- carrying shaft 11 and, thus, on the nut which is to be loosened, when the impact surface 8 of the hammering mem¬ ber hits the impact surface 14 of the projection 13a adja- cent the outermost end of the projection. The impact force then produced will probably cause the nut to come loose - otherwise the tool is further rotated around the nut, and the above-mentioned operating sequence is repeated. Figs 1-3 illustrate the position of the impact mechanism when the nut has come loose.

It is also possible to effect further pushing back of the hammering member by arranging additional cam means on the cam means 9 and 15 shown in the Figures, as described above. During continued rotation beyond the situation illustrated in Fig. 5, the additional cam means on top of the cam means 9 arranged on the hammering member will then engage the additional cam means arranged on the cam means of the wheel device. These additional cam means preferably have a shape similar to that of the cam means 9 and 15 illustrated in the drawings, and the hammering member 7 is disengaged in the corresponding manner as described for Fig. 5. If desired, even more coacting cam means in the same plane can be mounted on subjacent cam means, as described above. However, it should be noted that the wheel device 4 and the cam means 15 should then be arrang¬ ed so that the projection 13 takes the position shown in Fig. 5, i.e. perpendicular to the path of the hammering member.

The impact tool according to the invention has now been described in connection with the loosening of a nut or the like. It is of course also suited for tightening the same. Then the tool-carrying shaft 11 is caused to project with its shaft end 12 from the bottom of the hous¬ ing 1 in order to be connected with the nut that should be tightened, cf. Fig. 2. After adjusting the desired spring force as described above, the handle 3 is turned in the direction of arrow 18, whereby the above-described impact force is produced - in this case for tightening the nut.

In view of what has been said above, it is obvious to a person skilled in the art that the impact tool according to the invention is also suited to replace a ratchet wrench in a set of spanners and may function as a dynamo- metric wrench.

The invention is not limited to that described above and illustrated in the drawings, but may be modified with¬ in the scope of the appended claims.

Claims

1. Impact tool comprising a substantially cylindri- cal housing (1) with a projecting, tool-carrying shaft (11), and a handle (3) connected with the housing (1) which accommodate an impact mechanism comprising a wheel device (4) which is rotatably mounted in the housing (1) and formed with projections (13), each having an impact surface (14), and striking means (5) comprising a ham¬ mering member (7) which has an impact surface (8), and a compression spring (6) mounted in said handle (3) and engaging the hammering member (7), the tool-carrying shaf (11) being attached to the centre of the wheel device (4), the impact surface of the hammering member (7) engaging the impact surface (14) of one projection (13) when the impact tool is unloaded, and during initial rotation of the housing (1) relative to the wheel device (4), when the handle (3) is operated for the purpose of rotation the tool-carrying shaft (11), whereby the spring (6) is tensioned when the shaft (11) is nonrotatable, and the impact surface (8) of the hammering member (7), after a fixed angle of rotation of the housing (1) relative to the wheel device (4), being disengaged from the impact surface (14) of said projection (13) and subsequently, by the bias of the spring (6), being caused to strike the impact sur¬ face (14a) of the succeeding projection (13a), c h a r ¬ a c t e r i s e d in that the hammering member (7) is supported in the handle (3) for rectilinear motion in the axial direction of the handle, that the wheel device (4) is formed with a limited number of projections (13, 13a), that the wheel device (4) is provided with superposed, projecting cam means (15) which are arranged in the direc¬ tion of rotation after each impact surface (14), and that the hammering member (7) is provided with a superposed, projecting cam means (9) for engaging the respective cam means (15) of the wheel device (4), when the impact sur- face (8) of the hammering member (7) is disengaged from the impact surface (14) of the coacting projection (13).

2. Impact tool as claimed in clam 1, c h a r a c ¬ t e r i s e d in that the hammering member (7), when said cam means (9, 15) during continued rotation of the housing (1) relative to the wheel device (4) are disengaged from one another, is adapted to strike said projection (13a) substantially perpendicular thereto and adjacent the outer portion thereof.

3. Impact tool as claimed in clam 1 or 2, c h a r ¬ a c t e r i s e d in that the outermost portion of each projection (13, 13a) forms an extension of the associated impact surface (14) for continued pushing back of the ham¬ mering member (7).

4. Impact tool as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that a separate, axially displaceable weight member is arranged between the hammering member (7) and the spring (6).

5. Impact tool as claimed in any one of the preceding claims, c h a r a c t e r i s e d by means for adjusting the bias of said spring (6).

6. Impact tool as claimed in any one of the.preceding claims, c h a r a c t e r i s e d in that said handle

(3) is fixedly attached to said housing (1).

7. Impact tool as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that said handle (3) is releasably attached to said housing (1).

8. Impact tool as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the tool-car- rying shaft (11) is axially displaceable in said wheel device (4).

9. Impact tool as claimed in any one of the preced¬ ing claims, c h a r a c t e r i s e d in that the wheel device (4) is formed with three projections (13, 13a), and that the cam means (9, 15) are designed in such a manner that the length of motion of the hammering member (7), when disengaged, is approximately as great as the radius of said housing (1).

10. Impact tool as claimed in any one of the preced¬ ing claims, c h a r a c t e r i s e d in that additional cam means are arranged on top of and, as seen in the direction of rotation, after said cam means (15) on the wheel device (4) and project therefrom, for engaging addi¬ tional cam means mounted on the cam means (9) of said ham¬ mering member (7).